Odontosyllis pentalineata, Verdes, Aida, Pleijel, Fredrik & Aguado, Teresa, 2011

Verdes, Aida, Pleijel, Fredrik & Aguado, Teresa, 2011, A new species of Odontosyllis Claparède, 1863 (Annelida, Syllidae) with re-descriptions of O. liniata Hartmann-Schröder, 1962 and O. gymnocephala Hartmann-Schröder, 1965, Zootaxa 3095, pp. 27-38 : 32-36

Odontosyllis pentalineata n. sp.

( Figs. 3 A–D, 4A–I, 5A–F)

Material examined. USA: holotype (SIO-BIC A2518) ( COI GenBank accession number JF903757 ), 7 paratypes (SIO-BIC A2519, SIO-BIC A2520, SIO-BIC A2521,SIO-BIC A2522, SIO-BIC A2523). La Jollapier, California, 3252.024’N 11715.437’W; intertidal pole. 20 August 2007. Coll. F. Pleijel. La Jolla pier, California, 3252.024’N 11715.437’W; 6 m deep, intertidal pole. 21 August 2007. Coll. F. Pleijel. Off La Jolla Cove, California, 3250.713’N 11717.058’W; 12 m deep, Macrocystis holdfast. 29 August 2007. Coll. G. Rouse. Birds Rock, La Jolla, California, 3248.367’N 11717.181’W; 18 m deep, Macrocystis holdfast. 2 February 2010. Coll. E. Kisfaludy. Birds Rock, La Jolla, California, 3248.324’N 11717.107’W; 18 m depth, Macrocystis holdfast. 2 February 2010. Coll. E. Kisfaludy. Off Windansea, La Jolla, California, 3250.26’N 11717.11’W; 15 m deep, Macrocystis holdfast. 15 October 2010. Coll. G. Rouse, P. Zerofski. Off Windansea, La Jolla, California, 3250.26’N 11717.11’W; 15 m deep, Macrocystis holdfast. 15 October 2010. Coll. G. Rouse, P. Zerofski.

Comparative material examined. Odontosyllis trilineata Imajima, 2003 . Japan: 2 paratypes (NSMT-Pol R469) Kannonzukadashi-Aoyamadashi, Amadaiba, 3512.6’N 13932.4’E; 77–80 m deep. 20 July 1959. Coll. Biological Laboratory of the Imperial Household.

Diagnosis. Odontosyllis with a distinct dorsal colour pattern consisting of five longitudinal black bands (medial, dorso-lateral and lateral) extending throughout body, a long pharynx with five large teeth directed backwards and two lateral plates, and compound chaetae with short bidentate, slightly spinulated blades.

Description. Holotype complete but posteriorly regenerating specimen, 15.1 mm long, 0.94 mm wide, with 71 chaetigers. Longest paratype, complete specimen, 19.2 mm long, 0.78 mm wide, with 93 chaetigers. Body shape, excluding parapodia, circular in section, ventrally flattened. Dorsum with five longitudinal black bands (medial, dorso-lateral and lateral) extending throughout body ( Figs 3 A–D, 4A). Conspicuous ventral colour pattern consisting of three longitudinal black bands (one medial and two lateral) extending throughout body, anteriorly weaker to segments 20–22, distinct thereafter; present in holotype and one paratype, residual in another paratype. Segments with two ciliary bands extending across dorsum ( Fig. 5 A, B), and one ciliary band extending across ventral part of each parapodium ( Fig. 5 C, D). Prostomium small, wider than long, rectangular to oval, with two pairs of reddish eyes in trapezoidal arrangement, anterior pair slightly larger; eye spots absent. Median antenna inserted medially on prostomium, longer than prostomium and palps together; lateral antennae inserted near anterior prostomial margin, about half as long as median antenna. Antennae slightly articulated ( Figs 3 D, 4A). Occipital flap pigmented, semicircular, covering posterior half of prostomium ( Figs 3 D, 4A). Palps broad, triangular, completely separated, similar in length to prostomium. First segment shorter than subsequent ones. Tentacular cirri similar in shape to antennae; dorsal pair about twice as long as median antenna, ventral pair shorter, similar in length to median antenna. Dorsal cirri of first chaetiger longer than tentacular cirri; second, third and fourth dorsal cirri similar in length to dorsal tentacular cirri. Subsequent segments with alternating long and short dorsal cirri, long cirri about twice as long as short ones, and short cirri twice as long as parapodial lobes. Ventral cirri pillow-shaped and short, proximally inserted. Parapodia conical, with thick pre- and postchaetal lobes ( Fig. 4 B), prechaetal lobes longer than postchaetal ones. Chaetal fascicle with 10–12 compound heterogomph falcigers in midbody parapodia, shafts distally spinose ( Figs 4 C–E, 5E, F). Compound chaetae with short bidentate blades, distal tooth larger than proximal one, blade edge with minute serrations, blades exhibiting inverse dorso-ventral gradation in length ( Fig. 4 C– E), blades about 11.3 µm in length dorsally, 20 µm in length ventrally on midbody. Parapodia with two tricuspidate aciculae ( Fig. 4 F). Pharynx long, through seven segments, surrounded by 10 papillae ( Fig. 4 G–I), with five teeth directed backwards and two lateral plates ( Fig. 4 H). Proventricle long and slender, through about 15 segments, with around 60 muscle cell rows ( Fig. 4 I). Pygidium regenerating, anal cirri absent. Paratypes with two anal cirri, similar in length and shape to dorsal cirri.

Remarks. Odontosyllis pentalineata n. sp., is characterized by a distinct dorsal colour pattern consisting of five longitudinal black bands, long pharynx with five large teeth and two lateral plates, and compound chaetae with short bidentate blades with small spines. Odontosyllis pentalineata n. sp., is similar to several species of Odontosyllis with compound chaetae with short bidentate blades. This group includes O. australiensis , O. brachydonta , O. ctenostoma , O. dugesiana , O. fragilis , O. fulgurans , O. gravely , O. guillermoi , O. longigulata Perkins, 1981 ; O. luminosa , O. phosphorea Moore, 1909 ; O. polycera , O. setoensis and O. trilineata (Table 1). Odontosyllis pentalineata differs from all these species by the number of teeth of the denticled arc, the length of the pharynx, and, especially, by the characteristic pigmentation.

The most similar species, O. trilineata from Japan, has similar dorsal pigmentation. However, O. trilineata has three longitudinal black bands along the body, instead of five. The compound chaetae and the morphology of the proventricle are also quite similar to those of O. pentalineata , with the proventricle of both species extending through about 15 segments. Nevertheless, O. trilineata differs from O. pentalineata by having a trepan with nine pharyngeal teeth and a short pharynx extending through four segments ( Imajima, 2003), instead of five pharyngeal teeth and a long pharynx extending through seven segments. Odontosyllis gravely (from Australia and south-east India) also has a similar pattern of pigmentation consisting of a median longitudinal black band and large lateral spots on each segment that might approach three longitudinal stripes. This species also resembles O. pentalineata in the shape of the compound chaetae and number of pharyngeal teeth. However, they differ in that O. gravely has long-bladed chaetae and a shorter pharynx extending through only three to four segments ( San Martín & Hutchings, 2006). Odontosyllis fragilis (from southern California) also has dorsal pigmentation, but consisting of a dorso-median row of pigment spots along body. In addition, O. fragilis differs from O. pentalineata by having a shorter pharynx extending through four segments without lateral plates and lacking spinulation in blades of compound chaetae ( Kudenov & Harris, 1995). Finally, O. pentalineata resembles O. australiensis (from Australia) in the shape of the compound chaetae and number of pharyngeal teeth, although it has wider blades and smaller proximal teeth and its pharynx extends through seven segments instead of two. Additionally, the preserved O. australiensis was described as yellowish, probably lacking a defined colour pattern ( San Martín & Hutchings, 2006).

Etymology. The specific epithet refers to the dorsal colour pattern of the new species, characterized by five longitudinal black bands extending along the body, one medial, two dorso-lateral and two lateral.

Figures

FIGURE 3. Odontosyllis pentalineata n. sp. A: Paratype BIO-SIC A 2520. Complete specimen, dorsal view. B: Paratype BIO- SIC A 2521. Complete specimen, dorsal view; C: Paratype BIO-SIC A 2519. Complete specimen, dorsal view. D: Paratype BIO-SIC A 2519. Anterior end, dorsal view.

FIGURE 4. Odontosyllis pentalineata n. sp. Holotype BIO-SIC A 2518. Drawn from preserved specimen. A: Anterior part, dorsal view; B: Midbody parapodium; C: Compound chaetae, anterior parapodium (chaetae arranged dorso-ventrally from left to right); D: Compound chaetae, midbody parapodium (chaetae arranged dorso-ventrally from left to right); E: Compound chaetae, posterior parapodium (chaetae arranged dorso-ventrally from left to right); F: Aciculae, midbody chaetiger; G: Pharynx and surrounding papillae; H: Denticled arc; I: Pharynx and proventricle; Scale A 1 mm; B 0.195 µm; C, E 20 µm; F 10 µm; G 2.08 mm; H 0.195 µm; I 2 mm.

FIGURE 5. SEM micrographs. Odontosyllis pentalineata n. sp. Holotype BIO-SIC A 2518. A: Midbody chaetigers, dorsal view; B: Dorsal ciliary band, midbody chaetiger; C: Midbody parapodia, ventral view; D: Ventral ciliary band, midbody parapodium; E: Midbody chaetal fascicle; F: Compound chaetae, midbody chaetiger.